An agricultural harvester known as a “combine” is historically termed such because it combines multiple harvesting functions with a single harvesting unit, such as picking, threshing, separating and cleaning. A combine includes a header which removes the crop from a field, and a feeder housing which transports the crop matter into a threshing rotor. The threshing rotor rotates within a perforated housing, which may be in the form of adjustable concaves and performs a threshing operation on the crop to remove the grain. Once the grain is threshed it falls through perforations in the concaves onto a grain pan. From the grain pan the grain is cleaned using a cleaning system, and is then transported to a grain tank onboard the combine. A cleaning fan blows air through the sieves to discharge chaff and other debris toward the rear of the combine. Non-grain crop material such as straw from the threshing section proceeds through a residue system, which may utilize a straw chopper to process the non-grain material and direct it out the rear of the combine. When the grain tank becomes full, the combine is positioned adjacent a vehicle into which the grain is to be unloaded, such as a semi-trailer, gravity box, straight truck, or the like; and an unloading system on the combine is actuated to transfer the grain into the vehicle.
To remove crop material from the field, the header of the combine harvester may be equipped with a cutter bar assembly having many sharp cutting elements that reciprocate sidewardly, relative to a forward direction of travel, to sever the crop material from the field before entering the feeder housing. The header may include a rotating reel with tines or the like to sweep crop material toward the cutting elements.
To closely follow the ground and produce a consistent cut stalk length, many agricultural harvesters have flexible cutting elements, such as cutter bars, which can flex during harvesting. Flexure of the cutter bar(s) can help compensate for terrain irregularity encountered by the header during travel across a field. Some flexible cutter bars may allow, for example, 3 inches of travel in either direction from a normal, unflexed position, allowing the flexible cutter bar to compensate for up to 6 inches of ground irregularity across a width of the header.
Recent trends in agricultural vehicles have resulted in agricultural harvesters with relatively wider headers to allow more crop material to be cut in each pass of the harvester, reducing the number of passes necessary to harvest the crop material on a field. For example, some headers may have a width of 45 feet or more. Increasing the width of the header has been done in a variety of ways, including having a main section of the header which couples to one or more wing sections.
While widening the header allows for fewer passes to completely harvest a field, several challenges are presented by the increased widening of the header. As previously described, some flexible cutter bars can compensate for up to 6 inches of ground irregularity across a width of the header. As the header becomes wider, it has been found that more ground irregularity compensation may be needed to allow the header to consistently follow the ground due to many fields having more than 6 inches of ground deviation across a width of 45 feet or more.
What is needed in the art is an agricultural header which can follow the ground at increasing widths of the header.